The quotes homeowners get for "a crack in the foundation" can differ by a factor of ten, and the reason is simple: the word crack covers three completely different problems. A shrinkage crack in a poured wall is a waterproofing job. A horizontal crack in a wall that's starting to bow is a stabilization job. A crack paired with a floor that's dropping is a structural job. Same word, three price worlds. Sorting out which one you have comes before any number means anything.
Concrete shrinks as it cures, so thin vertical cracks in poured walls are common and usually harmless. The pattern, width, and direction tell you which category you're in:
| What you see | What it usually means | Typical response |
|---|---|---|
| Vertical or slightly diagonal crack, under 1/8 inch, dry or weeping slightly | Shrinkage or minor settlement | Injection repair, $300–$800 |
| Stair-step crack through block mortar joints | Settlement or soil pressure, worth monitoring | Monitor, then engineer if it grows |
| Horizontal crack in a block or poured wall | Lateral soil pressure pushing the wall in | Engineer, then straps or wall anchors |
| Crack wider than 1/4 inch, or one side offset from the other | Active movement | Engineer before any repair quote |
| Cracks plus doors sticking, floors sloping, gaps at trim | Settlement affecting the whole structure | Engineer; underpinning may follow |
| Crack in the basement floor only, level and dry | Slab shrinkage — usually not structural | Seal it yourself; see below |
Two quick home tests help. First, mark the ends of the crack with a pencil and date the marks; a crack that grows past them over a season is still moving. Second, check the crack against the rest of the house. Cracks that mirror themselves in the drywall above, or that line up with the sloping floors in an old house, are telling one connected story. Isolated hairlines in the basement, with nothing showing upstairs, are usually telling a much smaller one. The drywall side of that comparison is covered in our guide to drywall cracks: normal or serious — the same width and direction rules apply, just on a cheaper surface.
Injection is the standard fix for a non-structural wall crack that's dry or leaking. The contractor seals the face of the crack, sets small ports along it, and pumps resin in at low pressure until the crack is filled through the full thickness of the wall. Two resins do two different jobs:
Epoxy cures hard and bonds the concrete back together, restoring much of the wall's strength across the crack. It's the pick for a dry crack where strength matters. Polyurethane foam expands on contact with water and stays slightly flexible, which makes it the pick for an actively leaking crack — it chases the water and seals it. Foam seals; it doesn't add meaningful strength.
Most single-crack injection jobs land between $300 and $800, depending on crack length, wall thickness, and whether the inside face needs drywall or paneling removed to reach it. A long crack, or one that needs excavation on the outside, prices higher. One warning that matters: injection seals a crack, it does not stop the wall from moving. Inject a crack that's still opening and you'll pay for the same crack twice — it'll reopen right beside the repair.
A horizontal crack usually means soil pressure is pushing the wall inward. Injection alone can't hold that back. Carbon-fiber straps (sometimes called staples or strips, depending on the system) are epoxied flat against the inside of the wall, running vertically across the crack zone, and they hold the wall against further inward movement. They're thin, they paint over cleanly, and they don't eat floor space the way steel I-beams do.
Installed cost typically runs $400–$800 per strap, and a bowing wall section commonly takes 4–8 straps spaced a few feet apart — so a real-world strap job often totals $2,000–$5,000. Straps stabilize; they do not straighten a wall that's already bowed. If the wall has moved more than about 2 inches, or keeps moving after straps, the conversation moves to wall anchors or partial rebuilding, and an engineer should be running that conversation.
When the footing itself is sinking — the crack is a symptom of the foundation dropping, not just the wall cracking — the fix is underpinning: steel piers driven or screwed down to stable soil or bedrock, then used to support (and sometimes lift) the footing. This is engineering-led work from start to finish. No reputable pier job starts without a diagnosis of why the soil failed, and this article deliberately stops at cost and diagnosis: pier placement, depths, and lift decisions belong to the engineer and the crew on site, not to a homeowner guide.
Price it by the pier. Push piers and helical piers typically run $1,000–$3,000 each installed, and a settling corner or wall section commonly needs 4–10 of them. That puts most real underpinning projects in the $5,000–$20,000 range, with whole-house jobs going higher. Get at least two pier plans in writing and compare the pier count, not just the total — a low quote with half the piers is not the same job for less money.
The engineer's report ($300–$600). Often required before a contractor will warranty structural work, and the document that keeps a $600 injection from being sold as a $12,000 pier job — or the reverse.
Access work. Removing and replacing finished drywall, paneling, or a finished basement ceiling to reach the crack can add hundreds to a few thousand dollars, and it's frequently line-itemed separately or excluded entirely.
Drainage correction. If water pressure caused the crack, fixing the crack without fixing gutters, grading, or a failed drain tile means the pressure comes back. Exterior drainage work ranges from a few hundred dollars for downspout and grading fixes to $2,000+ for drain work.
Permits and inspections. Structural repairs need permits in most jurisdictions. If a quote has no permit line, ask why.
The honest DIY end of this topic is narrow. Sealing a level, dry crack in the basement floor slab is homeowner work — our guide to fixing a basement floor crack covers the sealant method and the monitoring that goes with it. Wall injection kits exist for $100–$250, and a patient homeowner can seal a simple, stable, weeping hairline with one. Everything past that — straps, anchors, piers, any crack that's moving — is pro work, because the cost of a wrong call isn't a redo, it's a wall.
Get the diagnosis in writing, separate from the price. What is moving, why, and what does the proposed repair actually do — seal, stabilize, or support? A quote that skips straight to products hasn't answered the first question.
Match the repair tier to the crack pattern. Injection quoted for a horizontal, bowing wall is under-scoped. Piers quoted for a dry hairline shrinkage crack is over-scoped. Both are red flags, in opposite directions.
Ask what the warranty covers. A lifetime warranty on a sealed crack usually covers the crack re-leaking — not the wall moving, not new cracks, not the floor. Read the exclusions before you weigh the warranty in the price.
Ask what happens if it moves again. The honest answer names the next tier up and roughly what it costs. A contractor who says it can't happen hasn't looked at enough foundations.
Most foundation cracks are the cheap kind: a few hundred dollars of injection, or a tube of sealant on a floor slab. The expensive kind announce themselves — horizontal, wide, offset, growing, or traveling with sticking doors and sloping floors. Read the pattern first, bring an engineer in when the pattern says movement, and match the repair tier to the diagnosis. The crack is the cheapest information your house will ever give you; the mistake is paying to cover it up before you've read it.
For the most common case — one non-structural wall crack sealed by injection — expect $300–$800. Carbon-fiber strap projects typically total $2,000–$5,000, and underpinning projects commonly run $5,000–$20,000 depending on pier count. The crack pattern, not the crack count, decides which range you're in.
A level, dry floor-slab crack, yes — flexible sealant handles it. A simple, stable wall hairline can be sealed with an injection kit for $100–$250. Horizontal cracks, wide or offset cracks, and anything still growing are not DIY: they point to movement, and sealing them hides the evidence without changing the cause.
Usually not. Gradual settlement, shrinkage, and soil pressure are typically excluded as wear and earth movement. A crack caused by a sudden covered event — a burst pipe washing out soil, for example — can be a different answer. Check your policy's earth-movement language before assuming either way.
Direction and behavior are the tells: horizontal cracks, cracks wider than about 1/4 inch, one side offset from the other, cracks that keep growing, and cracks that show up alongside sticking doors, sloping floors, or gaps at window trim. Any one of those earns a structural engineer's assessment before repair money gets spent.
They do different jobs. Epoxy cures rigid and restores strength across a dry, stable crack. Polyurethane foam expands to seal an actively leaking crack and stays flexible, but adds little strength. A good contractor picks based on whether the crack is wet and whether strength matters — and tells you which one they're using and why.